1. Field of the Invention
The present invention relates to novel, moldable thermotropic aromatic copolyesters prepared from (i) at least one substituted hydroquinone, or derivative thereof, (ii) a mixture of aromatic dicarboxylic acids, or derivatives thereof, and (iii) at least one aromatic carboxylic hydroxyacid, or derivative thereof.
2. Description of the Prior Art
Thermotropic polyesters are known to this art which are prepared from one or more diphenols and one or more aromatic and/or cycloaliphatic dicarboxylic acids. Polyesters of this type are disclosed, for example, in French Pat. No. 2,270,282; among the polyesters described therein, those prepared from a substituted hydroquinone, or derivative thereof, from terephthalic acid, or derivative thereof, and from 4,4'-dicarboxydiphenyl ether, or derivative thereof, are species of considerable interest.
Because of economic reasons and the high cost of raw materials, considerable research has been carried out by the assignee hereof to replace a portion of the most costly reactants, namely, the substituted hydroquinone or derivative thereof, and 4,4'-dicarboxydiphenyl ether or derivative thereof, with a compound of the hydroxyacid type, which is less costly and is readily commercially available. Such research has also sought to overcome a disadvantage of these particular copolyesters, namely, that the final mechanical properties are inadequate and need to be improved, especially the torsional and/or tensile and/or flexural moduli and/or the resilience values thereof.